It has previously been proposed to provide portions of flexible polymeric sheet material with different functions or physical properties. For example, in U.S. Pat. Nos. 6,394,651 and 6,394,652 it has been proposed to emboss such sheet material in different ways in order to give different portions of the sheet material different stretch properties.
It has also been proposed to treat portions of the surface of flexible polymeric sheet material in different ways in order to provide those portions with different functions or physical properties. In one proposal, US 2005/0227844 discloses a vacuum packaging bag in which at least one wall has hot-printed rough stripes on its inner surface, which are substantially rectilinear and extend longitudinally, preferably over the full length of the bag. The purpose of the rough stripes is to prevent sticking or adherence between parts of the bag and therefore to readily permit extraction of air from the bag during vacuum packaging.
In another proposal for surface treating portions of flexible polymeric sheet material to provide different functions or physical properties, WO 2004/060241 discloses striped material that is formed by depositing particles in stripes on a polymeric substrate. The striped material is described as particularly suitable for use in disposable absorbent articles such as napkins and diapers, and it is suggested that the particles may provide absorbency, odour-control, fluid modification, or various other functions or physical properties in response to substances that contact the striped material.
In all of the aforementioned proposals, the substrate flexible polymeric sheet material is the same throughout its extent, and the different functions or physical properties in different portions of the sheet material are provided by post-treating the substrate material.
Striped bags of two different colours are also known. Such bags are welded from extruded flexible polymeric sheet material formed from the same substrate composition but with alternating pigments in adjacent co-extruded bands to provide merely a visual difference between the stripes.
It would be advantageous to be able to provide a greater range of different functions or physical properties in different portions of extruded flexible polymeric sheet material and/or to provide different functions or physical properties in different portions of extruded flexible polymeric sheet material without having to post-treat the substrate sheet material. In some embodiments, it would also be advantageous to be able to provide modified functions or physical properties in extruded flexible polymeric sheet material, and products made therefrom, without having to use relatively expensive polymeric materials or additives throughout the sheet material. This may facilitate the use of relatively expensive components of the sheet material in price sensitive products such as disposable plastic bags.